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Process And Apparatus For Preparing Uniform Size Polymer Beads - Patent 4444961


The present invention relates to the preparation of spheroidal polymer beads, particularly to a method and apparatus for preparing spheroidal polymer beads having a relatively uniform particle size.A wide variety of polymers including polymers of a monovinylidene aromatic such as styrene or esters of an unsaturated carboxylic acid such as acrylic or methacrylic acid esters are prepared in spheroidal bead form using suspension polymerizationtechniques. Conventionally, suspension polymerization consists of dispersing a monomer as droplets in a vessel equipped with an agitator and containing a continuous phase in which the monomers and resulting polymer are essentially insoluble. Thedispersed monomer droplets are subsequently polymerized while maintaining continuous agitation.Unfortunately, the spheroidal polymer beads prepared by conventional suspension polymerization techniques exhibit a relatively broad particle size distribution. This is generally undesirable for the reason that spheroidal polymer beads employedin most applications advantageously exhibit a generally uniform particle size. For example, the ion exchange resins prepared from copolymer beads of a monovinylidene aromatic and a polyvinylidene aromatic advantageously exhibit a narrow particle sizedistribution to provide the desired flow characteristics to an ion exchange resin bed comprising said resin. Therefore, a significant percentage of the polymer beads prepared using conventional suspension polymerization techniques possess particle sizesundesirable for their intended application. Such undesirably sized beads are normally wasted or employed in applications of less economic desirability.Heretofore, various suspension stabilizers (suspending agents) have been employed to help improve the uniformity of the polymer beads prepared using conventional suspension polymerization techniques. (See, for example, U.S. Pat. Nos. 3,728,318 and 3,862,924.) While the suspending agents effectively maintain

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